1. Field of the Invention
This invention relates to a magnetoresistive effective element, a thin film magnetic head, a magnetic head device and a magnetic recording/reproducing device.
2. Related Art Statement
With the rapid advance in high density recording for hard disks (HDDs), performances of thin film magnetic heads have been enhanced on vast researches and developments and then, follow the high density recording performances of the HDDs. As the thin film magnetic head is usually employed a composite type thin film magnetic head comprised of a reading element made of a magnetoresistive effective element (hereinafter, called as a “MR element”) and a writing element made of an inductive type electromagnetic conversion element.
The MR element is mainly composed of a giant magnetoresistive effective film (hereinafter, called as a “GMR film”) such as a spin valve film (hereinafter, called as a “SV film”) and a ferromagnetic tunnel junction film (hereinafter, called as a “TMR film”). As the MR element with the SV film can be exemplified a CPP-GMR (Current Perpendicular to a Plane of a Giant Magnetoresistance) where a sense current is flowed perpendicular to the plane of the SV film, in addition to a typical GMR where a sense current is flowed parallel to the plane of the SV film.
Such a GMR film includes a pinned layer of which the direction of magnetization is pinned, a non-magnetic layer, and a magnetic response layer (hereinafter, called as a “free layer”) of which the direction of magnetization responds to an external magnetic field. When the magnetization of the free layer is rotated by the external magnetic field, the resistance for sense current through the non-magnetic layer is varied on the relative angle between the pinned magnetization of the pinned layer and the rotatable magnetization of the free layer.
The GMR element requires a magnetic shielding structure so as not to be affected by the disturbance in the external magnetic field because the GMR element has huge rate of MR change. In this point of view, it is proposed to sandwich the MR film with a first and a second magnetic shielding films. The distance between the shielding films is generally called as a “shield gap”.
Conventionally, the first and the second magnetic shielding films are generally formed with separated from the GMR film, but with the advance of high density recording, it is required to still narrow the shield gap. In this point of view, recently, it is mainly proposed that a pair of electrode films for flowing a sense current in the GMR element are made of conductive ferromagnetic material, and thus, also serves as the first magnetic shielding film and the second magnetic shielding film (cf., Patent Publication No. 3).
In the use of both the electrode films and the magnetic shielding films, the magnetizations of the magnetic shielding films may be changed due to the recording magnetic field, the magnetic field generated from the sense current in the GMR film and the like except the reading magnetic field generated from a magnetic recording medium, and thus, the GMR film may be affected by the change in magnetization of the magnetic shielding films. As a result, the reproducing output of the GMR element may become unstable and asymmetry fluctuation may be spawn. In a conventional thin film magnetic head with the above-mentioned GMR element, therefore, the fluctuation ratio of the reproducing output can be reduced only to 5.0%.
Patent Publication No. 1:
Japanese Patent Application Laid-open No. 2000-262519 (FIGS. 1-6)
Patent Publication No. 2:
Japanese Patent Application Laid-open No. 2001-6127 (FIG. 1)
Patent Publication No. 3:
Japanese Patent Application Laid-open No. 2002-117510 (FIGS. 4 and 5)